The present invention relates to a control device for an on-vehicle electric compressor.
A control device for an on-vehicle electric compressor drives and controls an electric motor of the on-vehicle electric compressor. The control device, for example, compares current corresponding to a temperature detected by a temperature detector with current detected by a current detector and uses the comparison result to control the rotation speed of the electric motor (refer to, for example, Japanese Patent No. 5039515).
Motor current, which is output from the control device for the on-vehicle electric compressor, flows to the electric motor. When the motor current increases, the amount of heat generated when power loss occurs in the control device for the on-vehicle electric compressor is apt to increase.
The on-vehicle electric compressor and the control device for the on-vehicle electric compressor are installed in a vehicle. Thus, the control device for the on-vehicle electric compressor may be exposed to a high-temperature environment. When the motor current is high under such a high-temperature environment, the temperature of the control device for the on-vehicle electric compressor may become excessively high and adversely affect the drive-control of the electric motor.
To cope with such a problem, rotation speed control may be performed as described in the above publication. However, since the load torque of the on-vehicle electric compressor changes in accordance with the travelling conditions or the like of the vehicle, the motor current may differ even when the rotation speed is the same. Thus, the execution of rotation speed control may not be able to restrict overheating of the control device for the on-vehicle electric compressor. Accordingly, there is room for improvement in the structure that restricts overheating of the control device for the on-vehicle electric compressor.